Petroleum in its natural state is considered a colloidal system constituted by four well defined organic fractions: 1) Saturated, 2) Aromatic, 3) Resins, and 4) Asphaltenes.
Asphaltenes are typically defined as the fraction of crude oil that is insoluble in low molecular weight aliphatic solvents such as n-pentane and n-heptane, but soluble in toluene, and that exist in the form of colloidal dispersions stabilized by resins.
From the structural point of view, asphaltenes are molecular aggregates of polyaromatic rings having small quantities of heteoratoms (sulfur, nitrogen and oxygen), traces of metal (iron, nickel and vanadium), linear branches having paraffinic characteristics and that remain primarily bound by π-π-type supramolecular interactions. Said structural characteristics entail that asphaltenes be the most polar fraction in crude oil and that they tend to precipitate upon abrupt temperature, pressure, or composition changes occurring at the extraction, transportation, or processing of crude oil.
The phenomenon of asphaltenes' precipitation in crude oil occurs when, at favorable temperature, pressure, and composition conditions, small asphaltene particles having low molecular weight associate, grow, and generate large and heavy asphaltene aggregates that become insoluble in the media. The large weight and the polar nature of these asphaltenes result in them diffusing towards the bottom of the oilfield's, pipeline or equipment, and adhering tightly to their walls. This phenomenon is known as asphaltene deposition.
Asphaltene deposition is directly related with: 1) Damage to the formation in oilfields, 2) Fouling and clogging of the hydrocarbon production wells and transportation ducts, and 3) Fouling occurring in the crude oil refining plants. Such problems cause great yearly losses to the oil industry.
Traditionally, in the petroleum industry, the fouling and clogging problems caused by the deposition of asphaltenes have been controlled by means of the use of asphaltene inhibitors and/or dispersants, which are comprised by two essential parts known as head and tail.
The head (the philic part) is a polar group whose function is to interact with the aromatic rings or the polar groups of the asphaltenes, whereas the tail (the phobic part) is an aliphatic chain that can be linear or branched and whose function consists in forming an esteric chain, which prevents the asphaltene molecules from getting too close to each other.
FIG. (1) shows that, by means of theoretical Monte Carlo simulations, it is possible to explain the way that the asphaltene aggregation process is controlled by the use of asphaltene inhibitors-dispersants.
In FIG. (1), the squares represent the asphaltenes' polar group (active site), the black and white circles represent the inhibitor-dispersant (head and tail, respectively), and the light-gray colored circles are the media (solvent). In our calculations we have assumed that the inhibitor-dispersant efficiency is directly related in a linear fashion with the concentration of asphaltene active sites “covered” (reacted) by the head of the inhibitor. The simulation calculation was carried out for two inhibitor-dispersant concentrations (A and B), where the concentration of A is lower than the concentration of B. In the simulation, two asphaltenes tending to agglomerate are represented as two surfaces having active sites at a certain H distance between them. These two parallel-located surfaces are immersed in a solvent to which a certain inhibitor-dispersant concentration is added in order to locally analyze its performance (head- and active site-association of an asphaltene).
As shown in part a of FIG. (1) (inhibitor concentration A), the head drives the inhibitor-dispersant to shift and bind to the asphaltene surface's active sites, where more than 50% of the inhibitors placed in the system remain adsorbed; additionally, it can be appreciated how the tail blocks some active sites, producing an steric effect.
However, in part b of FIG. (1) (concentration B) it can be observed that, upon increasing the inhibitor-dispersant concentration, the formation of a micelle-aggregate comprised by inhibitor-dispersant molecules occurs, and the affinity of the head to link with an active-site of the asphaltene markedly decreases, leaving its surface almost free.
Hence the importance that the adequate selection of the functional groups conforming the head of the inhibitor-dispersant molecule has, as well as the care given to the design of its structure, in order that the head links with the asphaltene active-site, and the tail forms an esteric barrier, while minimizing unwanted supramolecular interactions, such as the formation of inhibitor-dispersant micelles at the same time.
As important examples in the literature, mentioning the development of chemical compounds and their applications in crude oil in order to inhibit or disperse asphaltene deposits, we can mention the international patents: U.S. Pat. Nos. 7,122,113 B2, 7,122,112 B2, 7,097,759 B2, 6,946,524 B2, 6,313,367 B1, 6,204,420 B1, 6,180,683 B1, 6,063,146, 6,048,904, 5,504,063, 5,494,607, 5,466,387, 5,388,644 y 5,021,498.
The U.S. Pat. No. 7,122,113 B2 refers to the use of dendrimeric compounds to solubilize asphaltenes present in a hydrocarbon mixture. Preferably, the dendrimeric compound is a hyperbranched amide polyester, preferably constructed based on succinic anhydride, diisopropanol amine, and functionalized with polyisobutenil succinic anhydride.
The U.S. Pat. No. 7,122,112 B2 refers to the development of compounds having the structural formula:
containing specifically carboxyl and amide groups within their structure, and their application as asphaltene dispersants in crude oil.
Within the structural formula (1), R5 is a difunctional alkyl group that can range from C1 to C70, and R3 and R4 are independent radicals that can be represented by aryl, alkyl, alkylaryl, heterocyclyl groups, or hydrogen. The patent also indicates that this type of compounds increases demulsibility, and reduces viscosity, sediment formation, fouling of surfaces, and corrosion.
The U.S. Pat. No. 7,097,759 B2 refers to the development of compounds having the structural formula:
specifically having in their structure a carbonyl, thiocarbonyl, or imine group, and their application as asphaltene dispersants in crude oil. Within the structural formula (2), R14 is an alkyl group that can range from C15 to C21. The patent also indicates that this type of compounds increases demulsibility, and reduces viscosity, sediment formation, fouling of surfaces, and corrosion.
The U.S. Pat. No. 6,946,524 B2 refers to a process to produce polyesteramides, by reacting a polyisobutylene with a first agent selected from the group consisting in monounsaturated acids having from 3 to 21 carbon atoms and derivatives thereof, and a second agent selected from the group comprised by monoethanolamine and alkylamines having the structural formula:R—NH2  (3)wherein R represents an alkyl group having from 1 to 4 carbon atoms. The resulting polyesteramides are used as asphaltene stabilizers in crude oil and crude oil derivatives.
The U.S. Pat. No. 6,313,367 B1 patent, mentions that several esters and ethers reaction products are excellent asphaltene inhibitors or dispersants and can be used in hydrocarbons such as crude oil. The asphaltene-inhibitor compounds can be: 1) esters formed from the reaction of polyhydric alcohols with carboxylic acids, 2) ethers formed from the reaction of glycidyl ethers or epoxydes with polyhydric alcohols, and 3) esters formed from the reaction of glydicyl ethers or epoxides with carboxylic acids.
The U.S. Pat. No. 6,204,420 B1 mentions the development of a new formulation where the asphaltene-dispersant action of carboxylic acids can be extensively enhanced by the addition of relatively small amounts of esters derived from alkyl phosphoric acids. The formulation comprises: A) 5 to 99% in weight of a carboxylic acid having more than 4 carbon atoms, an ethercarboxylic acid bearing C18-C22 alkylic, C18-C22 alkenylic, or C6-C18 alkylarylic substituents, an amide-carboxylic acid or a mixture thereof, and B) 1 to 95% in weight of a mono- or di-phosphoric ester or a mixture thereof, which is substituted by a C18-C22 alkylic, a C18-C22 alkenylic, a C6-C18 alkylarylic or an alkoxylated group, wherein the sum of A and B is 10% in weight.
The U.S. Pat. No. 6,180,683 B1 mentions the development of a new formulation having a synergistic effect as an asphaltene dispersant. The formulation comprises 5 to 95% of a compound A having the structural formulae I or II:
and with 5 to 95% in weight of a compound B having the structural formula III:

The formulation is an excellent asphaltene dispersant in crude oil and crude oil-derived products.
Within the structural formulae I and II on (4), n is within the range from 2 to 12, preferably from 5 to 9, and R is a C3-C24, preferably a C4-C12 alkyl group, particularly isononil, isobutyl or amyl, or a C6-C12 aryl group or a C7-C12 alkylaryl group or an hydroxyaryl group.
Within the structural formula III in (5), n and m are independent from each other, and are numbers within the range from 0 to 120, preferably from 5 to 80, with the sum of m and n yielding at least 5. Z is an integer ranging from 1 to 4, preferably 4, and A is a radical containing amine groups within its structure.
The U.S. Pat. No. 6,063,146 refers to the use of ethercarboxylic acids having the structural formula:
as asphaltene-dispersants in crude oil and crude oil-derived products.
Within the structural formula (6), R is a C6-C22, preferably C9-C18 alkyl group, or a C6-C20 alkylaryl group. Z1 and Z2 are independent from each other, and can be H or a methyl group, preferably H. n and m are independent numbers between each other, and lie between the range from 0 to 20, the total of n and m falling within the range from 1 to 20, preferably from 1.5 to 8.
The U.S. Pat. No. 6,048,904 mentions the use of branched alkylaromatic sulfonic acids having the structural formula:
used as asphaltene dispersants in crude oil and crude oil-derived products.
Within the structural formula (7), R and Q are alkyl chains having a length ranging from 16 to 30 carbon atoms with at least one branch of a methyl group or longer alkyl groups.
The U.S. Pat. No. 5,504,063 mentions that a formulation formed by the product of the condensation reaction of a fatty acid, an alkylene amine, and one or more polar aprotic solvents having a high dielectric constant is useful for removing and inhibiting asphaltene deposits from wells, ducts, and associated equipment.
The U.S. Pat. No. 5,494,607 mentions that alkyl mono- or di-substituted phenol-formaldehyde and/or alkyl monosubstituted phenol-polyethylenepolyamine-formaldehyde resins are useful as asphaltene dispersants in crude oil and crude oil-derived products. Said resins have an average molecular weight ranging from 1000 to 20000 and the substituent alkyl contains from 4 to 24 carbon atoms and can be linear or branched.
The U.S. Pat. No. 5,466,387 mentions that crude-soluble additives with dispersing properties are prepared by reacting an alkyl or alkenyl disuccinimide with an unsaturated bicarboxylic aliphatic acid or the corresponding acid. The reaction is carried out at a temperature ranging from 130 to 170° C.; the anhydride-to-disuccinimide molar ratio ranges between 1.05 and 1.95.
The U.S. Pat. No. 5,388,644 mentions a method to reduce, preferably to prevent, the precipitation of asphaltenes in crude oil. In a first stage, the crude oil comes into contact in the drill with at least an N,N-dialkylamide derived from a fatty acid having from 8 to 22 carbon atoms. In a second stage, the precipitation is reduced during the miscible injection in a recuperation process enhanced by adding at least one N,N-dialkylamide derived from a fatty acid having from 8 to 22 carbon atoms to the injected solvent. The N,N-dialkylamides derived from fatty acids are represented by the structural formula:R3C(O)—N(R1)(R2)  (8)
Within the structural formula on (8), R1 is a substituted or non-substituted alkyl group located between C1-C6, R2 is a substituted or non-substituted alkyl group located between C1-C6, and R3(C(O) is a residue of a substituted or non-substituted fatty acid with 8 to 22 carbon atoms.
The U.S. Pat. No. 5,021,498 mentions that a mixture of an alkyl substituted phenol-formaldehyde resin with a hydrophilic-lipophilic vinylic polymer acts as an asphaltene and asphalt dispersant in crude oil. The alkyl substituted phenol-formaldehyde resin has an average molecular weight ranging from 1000 to 20000, the alkyl substituent contains from 4 to 24 carbon atoms and it may be linear or branched, and the weight percentage of said resin in the mixture can range from 10 to 100. The weight percent of the hydrophilic-lipophilic vinylic polymer in the mixture can range from 10 to 100.
The present invention markedly surpasses the aforementioned references since it consists of additive formulations containing as their main component an oxazolidine derived from polyalkyl or polyalkenyl N-hydroxyalkyl succinimides, capable of acting both as asphaltene inhibitors and dispersants to be used in crude oil or products derived thereof in order to control fouling and/or clogging problems occurring in production, transportation, refining, and storage processes related with the petroleum industry. These formulations distinguish themselves with respect to the commercial products evaluated for this double function because, even when one of them showed a comparable or slightly superior capability in the dispersion tests, it was clearly surpassed, as were both the other products, in the precipitation and deposition inhibition tests.